'reflection', aka traversing symbol tables

d_i_r_t_y has asked for the wisdom of the Perl Monks concerning the following question:

in each of my 258 perl modules i have a line like the follwing, corresponding to the current CVS revision:

our $CVS_REVISION = q!$Id: Action.pm,v 1.62 02/4/4 03:16:10 matt $!;
[download]

i'm trying to write a debugging routine which iterates over the keys of %INC (ie: to get the list of currently loaded modules), looking for the existence of this very $CVS_REVISION variable. I have been trying to use symbolic references (such as the code below) to achieve this, so far unsuccessfully. can anyone correct me?

{
    no strict;
    local $^W = undef;

    my @versions = ();
    foreach my $class ( sort keys %INC ) {

        $class =~ s/\.pm$// or next;
        $class =~ s/\//::/g;

        my $version = ${"$class\::CVS_VERSION"} || next;
        push @versions, "$class -> $version";
    }
}
[download]

cheers, matt

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Re: 'reflection', aka traversing symbol tables by Zaxo (Archbishop) on Apr 06, 2002 at 07:48 UTC
You're applying your matches to the names, not the files. Keep strict and warnings, here's a fairly cheesy approach: my $cvs_match = qr/whatever/; for (keys %INC) { push @versions, ($foo = `perldoc -m $_`) =~ /$cvs_match/; } [download] Sorry that's not the whole job, but it's an outline. After Compline, Zaxo	[reply] [d/l]
Re: Re: 'reflection', aka traversing symbol tables by d_i_r_t_y (Monk) on Apr 06, 2002 at 08:33 UTC
thanks for your reply. i should have included some context info. what i want to do is to be able to print the values of each module's $CVS_REVISION variable at the time that the source was initially parsed by Perl (which may be a different value than when this function is called). The intent is that i'd like to know what CVS versions of each module are being run in the currently executing mod_perl application. cheers, matt	[reply]
Re: 'reflection', aka traversing symbol tables by rjray (Chaplain) on Apr 06, 2002 at 08:47 UTC
I would suggest having a look at the code in the Apache::Status module, which comes with `mod_perl`. It does a lot of stuff similar to this, and you're certain to find a few pieces of code that are useful to lift and adapt to your own needs. `--rjray`	[reply]
ITYM by Fletch (Bishop) on Apr 06, 2002 at 13:40 UTC
`my $version = ${"${class}::CVS_VERSION"} \|\| next;` [download] That's a bit more standard, and it's clearer what you mean ( what's in `$class` follwed by "::CVS_VERSION" rather than `$class::CVS_VERSION`) than just backwhacking the colon.	[reply] [d/l] [select]
Re: 'reflection', aka traversing symbol tables by Anonymous Monk on Apr 06, 2002 at 21:46 UTC
You're going to kick yourself :-) You said you're looking for values of `$CVS_REVISION`, but your code looks for values of `$CVS_VERSION`.	[reply] [d/l] [select]